Abstract: In this study, the 500 hPa geopotential height fields of the Northern Hemisphere based on the NCEP/NCAR reanalysis data, the ERA-40 of the ECMWF data and the China NMC data which are compiled according to the observations from the weather stations integrated with the routine data collecled by the Central Weather Service of China were be compared for the period 1957-2002.The differences of these data in the four seasons were depicted and discussed using statistical analysis methods. The main purpose of this study was to reveal the NCEP data adaprability and reliability in East-Asia. The reaults show that some obvious differences exist in either the mean fields or the correlation fields between the NCEP/NCAR reanalysis data and ERA-40 of the ECMWF data. The largest difference centers were located in the East-Asia, especially in the area from south of the Baikal Lake to northwest and middle of China (30°-50°N, 80°-115°E). The largest differences were in summer and the most interrelated season was winter for the period 1958-1970. In the meantime, the NCEP/NCAR reanalysis data shows an unusual low value compared with the ERA-40 of the ECMWF data during 1958-1962 with a obvious in crease from 1962 to 1969 followed. In contrary, both the ERA-40 of the ECMWF data and the China NMC data show no such anomolies. As a result, it is suggested that we should pay more attention to what range and season to be addressed when using the NCEP/NCAR 500 hPa reanalysis data on the East-Asia, especially on the area from south of the Baikal Lake to northwest and middle of China (30°-50°N, 80°-115°E) in Spring and Summer. As a matter of fact, the data since 1970s are the most desirable. On the other hand, the ERA-40 of the ECMWF data and the China NMC data are coincident with each other to a great extent on this area above during 1960s to 1970s, implying that both of them are more reliable.